Testing apparatus



Nov. 26, 1935.

I C. A. ANDERSON TESTING APPARATUS -Filed Jan. 2. 19 32 InventorClarence Fl. Hndzrsun Patented Nov. 26, 1935 UNETED STATES TESTINGAPPARATUS Clarence A. Anderson, Chicago, Ill., assignor to 1 AssociatedElectric Laboratories, Inc., Chicago,

111., a. corporationof Delaware Application January 2, 1932, Serial No.584,429

3 Claims. (01. 175-183) This invention relates to testing apparatus ingeneral, and particularly to apparatus for locating faults in electricaldistribution systems. The object of the invention is to provide asimpleand reliable device for indicating the location crosses betweenconductors of such systems and adjacent metal framework.

The invention is particularly suitable for cating crosses between thelighting circuit conductors and the frames orshells of steel railwaycoaches, between the lighting or ignition system conductors and thechassis of motor vehicles, and between cable conductors and metalframework or runways of telephone exchanges, etc. By way of illustrationthe operation of the apparatus constituting the invention will bedescribed in connection with railway coach testing.

Referring now to the accompanying drawing, Fig. 1 shows the circuitarrangement of the tone generating set TS, a pick-up coil PC, and a partof the wiring system of a railway coach. Fig. 2 is a cross-sectionalView of a test lamp for use in conjunction with the test set.

The tone generator, Fig. 1, produces a tone current similar to thatproduced by the hand operated tone generator disclosedin applicant'sPatent No. 1,384,734, granted July 19, 1921. It consists of a magnetogenerator G driven by the motor M through the shaft i and coupling C. Ametal collar 2 fitted on the shaft and in electrical contact therewithis engaged by brush 1, which serves as one terminal of the generator.Collar 3 is also fitted on the shaft and is made of fibre or otherinsulating material. The metal pin 4 extends through the collar andshaft, protruding slightly on each side whereby it engages brush 8 oneach half revolution of the shaft. Brush 5 is mounted on the generatorframe but insulated therefrom, and. serves as the other terminal of thegenerator. Brushes 5 and 8 are directly connected so that the generatoris shortcircuited each time the latter brush engages pin 4.

Terminal posts l9 and are provided for connecting the tone generator toa circuit under test. Terminal post I9 is connected by way of conductorl8 to brushes 5 and8 and these in turn are connected to the upperterminals of transformer T by way of conductor Ill. Terminal post 20 isconnected to the sleeve of jacks J and J! by conductor 23. A plug P isprovided for connecting this terminal directly with the frame terminalof the generator or with the secondary winding of the transformer.Itwill be noted that with plug P in jack J, terminal 20 is connected byway of conductor l6 and condenser I! to brush 1, while the circuit ofwinding ll of the transformer is open at contacts i3. It is apparentthat under these conditions, with the generator operating, condenser I!will be charged 5 in series with the external circuit connecting theterminals l9 and 26 and will periodically disa railway coach. An innershell consisting of 20 plates such as 5? is separated from the outershell by suitable spacing members (not shown). The lighting systemconductors are carried through the space between the inner and outerplates from the distributing panel to the light sockets located invarious parts of the car. A separate circuit is ordinarily provided foreach group of lights. The distributing panel is provided with two busbars B and BI, connected,

respectively, to the two terminals of the car 30 storage battery asindicated. The lighting conductors are connected to the bus bars byremovable fuses, such as 59 and Gil, which are shown connecting upconductors 53 and 54. The particular lighting circuit shown by way ofillus- Itratingthe operation of the invention consists of conductors 55and 55 which serve a group of lamps including the lamp L. Theseconductors are connected by branch circuits with the various lightsockets of which only the socket S 4.0

has been shown.

The pick-up coil PC consists of a coil 24 wound on an iron core 25. Thecore is rigidly attached at one end to a handle 23 of fibre or othersimilar material to which the terminal pins 26 and 5 21 are attached. Atip 29 of fibre protects the other end of the core and coil from injury.The

7 terminals of the coil are brought out to the pins 26 and 21., which inturn are connected to the receiver R by means of a flexible cord 39.

rapidly fluctuating, a current will be induced in the winding andproduces an audible tone in the receiver.

The test lamp, Fig. 2, as will be readily seen 55 When this coil isbrought into a magnetic field which is from the drawing, is made up of afibre tube 3| with a metal liner or inner tube 32. Within this tube asmaller tube of fibre 33 is held in place by the fibre blocks 34 and 35.Metal rods 36 and 3'! are fitted into opposite ends of the small fibretube and are held in place by screws 38 and 39 which also serve to holdthe tube firmly attached to the fibre blocks. Inside the fiber tube 33there is a laminated iron core 33 which is insulated from the metal rods35 and 31 by fiber discs 35 and 31'. The laminated core 33 is not shownin section and may consist of iron wires or the like. The tube 33 hasbeen cut away to show the iron core and the coil 44 is clearly shown onthe center part of tube 33. Rod 38 is electrically connected by screw 38and metal piece 38' to one end of the coil 44 which is wound on thesmall fibre tube, the other end of the coil being connected by way ofscrew 39 and metal piece 39' to metal rod 31. Rod 31 incidentallyprotrudes slightly beyond the fibre block 35 and is adapted to engage aconductor to be tested. Spring 48, fitted into the end of rod 36,engages one contact of lamp 4!. This lamp may be of the type ordinarilyused in three cell flash lights, and is held in the metal socket 42,which is threaded to permit screwing into the inner tube 32. A screw 43provides a terminal for connecting a source of current to the metal tube32. It will be seen from the foregoing that a circuit for lighting thelamp extends from the generator terminal connected to clip 5!, terminal43, tube 32, socket 42, lamp 4|, spring 40, rod 36, screw 38, resistancecoil 44, screw 39, tip of rod 31, and the conductor in contacttherewith, which is connected to the other terminal of the generator.

In actual railway operation, it has been found that the lightingcircuits very frequently become crossed on the metal framework of thesteel railway coaches. These faults usually occur around the lampsockets, but, due to the hidden wiring, it is extremely difficult tolocate them. Further, disconnecting the various sockets and testing themindividually is a slow and expensive job. This method of testing,however, has been the only practical one with testing apparatusheretofore available.

With the present testing device, frame crosses in car lightingsystems ofthe above type may be located easily and quickly without disturbing anyof the sockets or wiring. To locate a fault, the motor is firstconnected across the bus-bars B and B! by means of the flexible ends 41and 48 and their terminating clips49 and 50. The motor drives thegenerator, which produces a distinctive tone current as previouslyexplained. If the particular conductor in trouble is not known, this isfirst located by means of the test lamp, Fig. 2. Clip 69, which isconnected to terminal post l9 by conductor 45, is attached to the metalshell of the car. Clip 5!, which is connected to terminal post 29 byconductor 46, is attached to terminal 43 of the test lamp. Plug P isinserted into jack J I, thereby bridging the secondary winding ofstep-down transformer T across the terminals l9 and 20. The fuseterminals of the lighting conductors are now touched successively withthe metal tip of the test pencil. When a circuit crossed with the frameis found, the lamp will glow brightly to indicate this condition. I-Iighresistance crosses will cause the lamp to glow dimly.

After locating the particular lighting conductor in trouble, clip 5| isdetached from the test lamp and attached to the fuse terminal of theconductor. Plug P is then shifted to jack J, thereby bridging thegenerator and condenser directly across terminals [9 and 29. By way ofillustration, it will be assumed that conductor 56 is shorted on theinner shell 51 of the car at the point 58 at which the conductor isconnected with socket S. The tone current will accordingly flow in acircuit including conductor 55 and plate 57. The current density in themetal plate will be greatest at the point of contact with the conductorand the magnetic field around this point will be proportionately large.If the finder coil, P. 0., is now held fairly close to plate 5'! at anypoint between clip 49 and socket S, the current flowing in the platewill induce a similar current in the coil 24, and a tone will be heardin receiver R. The coil is then moved away from the clip, and, when itarrives in the vicinity of the fault, the tone will increase rapidly,the point of maximum tone indicating the exact point at which theconductor is short circuited on the frame.

The method of locating faults in the lighting or ignition systems ofmotor cars or similar vehicles is substantially the same as that abovedescribed for railway coach testing. One terminal of the generator isconnected to the metal frame of the vehicle and the other terminal isconnected to the faulty conductor. The finder coil is then moved aboutin the vicinity of the frame until the point is formed at which the tonein the receiver is loudest. The method of locating faults in telephoneexchanges and the like will be readily apparent.

What is claimed is:

1. A testing device comprising a tone generator,

a pair of terminals for connecting the device with a circuit to betested, a transformer, a pair of manual jacks, a plug for cooperationwith either jack, circuit connections completed upon the insertion ofthe plug into one of said jacks for connecting the generator to saidterminals directly, and other circuit connections completed responsiveto the insertion of said plug into the other of said jacks forconnecting the generator to said terminals through said transformer.

2. A testing device comprising a generator, a transformer having itsprimary and secondary windings both normally connected across thegenerator, two terminals, two switches, circuit connections controlledby one switch for disconnecting the primary winding of the transformerfrom the generator .and for connecting the generator directly acrosssaid terminals, and circuit connections controlled by the other switchfor disconnecting the secondary winding of the transformer from thegenerator and for connecting it across said terminals.

3. An electrical testing device comprising a generator, a condenser, atransformer having its primary and secondary windings both connectedacross the generator in series with said condenser, a pair of terminals,2. switch for disconnecting the primary winding of the transformer fromthe generator and for connecting the generator and condenser in seriesacross said terminals, a second switch for disconnecting the secondarywinding of the transformer from the generator and for connecting itacross said terminals.

CLARENCE A. ANDERSON.

